The present invention is directed toward providing a method for removing spilled crude oil, or other oil products, from the open environment. More particularly, this invention relates to the use of a biodegradable substance having a strong affinity for oil to efficiently remove crude oil from an aqueous medium.
Crude oil, and other derivative oil products, can cause severe environmental damage when spilled into the open environment. Because of the environmental danger, comprehensive means for removing the oil are necessary to remedy the mishap and prevent further environmental degradation. This is a problematic and expensive task, which is further frustrated by the fact that oil spills are unexpected events requiring immediate action and readily available supplies. Spill disasters occur under a variety of circumstances, and efficient methods for clean-up are often learned as the operations proceed. Several techniques have been found to have utility in a variety of circumstances. However, the usefulness of these methods, and combinations thereof, varies depending upon the location and size of the spill, as well as the environmental conditions present at that time.
Many oil spills occur in navigable waters and several clean-up methods have been developed to remove oil from aqueous environments, which include the use of fire, dispersants, mechanical booms and skimmers, and absorbent materials. The least environmentally damaging method of clean-up is supplied by mother nature in the form of microorganisms that metabolize oil on land and in the water. These organisms are not generally concentrated in a spill area to the extent needed for fast and comprehensive cleanup.
Although spills into navigable waters are hazardous to wildlife, and a general threat to healthy ecosystems, there is even greater environmental concern when oil reaches delicate coastal areas, shellfish beds, or land areas which provide habitat for wildlife. Therefore, preventing the spread of spilled oil over a larger expanse of water or onto adjacent land areas is a primary objective in most clean-up operations.
Burning or the use of dispersants is often first looked to as a clean-up method when a spill is large and has not spread into coastal regions. Burning does have utility in ridding the aqueous region of the oil quickly, thereby preventing further spread of the oil to more delicate areas. However, the more volatile components of crude oil evaporate quickly so that large quantities of a wicking agent are needed to keep the oil aflame. Burning has limited success in cold environments, because the water temperature removes heat faster than combustion can be supported. Although burning can prevent environmental damage by removing oil from the aqueous environment, the amount of resulting air pollution diminishes its overall utility.
The use of dispersants is a more recent method for cleaning up oil spills, which is predominantly considered in the initial stages of clean-up procedures to prevent spreading of oil into more delicate areas. Dispersants penetrate an oil slick and form an oil in water emulsion, so that the oil is dispersed into small droplets throughout a larger volume of water. The oil is not actually removed from the water. Instead, the increased oil surface area permits much more evaporation and microbial activity so that the oil will presumably disappear in time. Dispersants are often used when a spill exists in outlying water areas. They have limited utility when the oil has spread near coastal regions, because freshly dispersed oil washes ashore and contaminates land areas. There is a strong environmental objection to the use of dispersants, because dispersants are primarily composed of solvents that are toxic to marine life.
Another method for preventing the spread of oil is the use of mechanical booms which are physical barriers that confine oil within boom perimeters. Booms have limited success, however, because the trapped oil often passes below the boom in the presence of large waves or strong currents. When booms are used to prevent spreading, then skimmers which mechanically pump or scoop oil out of the water are often used to remove the confined oil. These two methods work well in combination to prevent spreading and to remove oil. Both have limited utility where a spill is large, because the boom barriers cannot confine a vast area and because the skimmers are slow and work best in areas where the oil layer is thick.
When there is a large spill, either thinly spread or near coastline regions, absorbent materials can be used as a method of removal. The absorbant material soaks up the oil and is later removed from the water, so that the oil absorbed is also removed. There are both natural absorbent materials including peat moss or straw and synthetic absorbents such as polyurethane. The natural materials are inert and biodegradable so they can be used in more delicate areas, whereas the synthetic materials have more buoyancy and affinity for oil so that more oil is removed. There is one very big problem with absorbents. It is the disposal of the oil soaked absorbent materials. Transporting the materials from the spill sight to proper disposal areas can be costly, and there is environmental concern over the use of incineration or other disposal methods to destroy the materials. Although recycling has found some success, particularly for synthetics, the problem is a big one.
When coastline land areas are affected, there has been some success with cleanup by using hot water and/or scrubbing. Hot water is applied under high pressure to "blast" the oil off shoreline rocks. The oil is diluted by the hot water running off into adjacent waters and is then removed by aqueous removal techniques. Scrubbing the shoreline rocks with absorbent materials is another choice and experimentation with microbial activity has proven somewhat successful. Due to the environmental sensitivity of these areas and costs associated with attempted clean-up, it is important to have additional methods that do not create further environmental risk but which also confine and remove oil in an efficient and comprehensive fashion.